DE102004009536A1 - Process for the preparation and structuring of a photosensitive, highly viscous, chemically amplified, aqueous alkaline developable positive photoresist - Google Patents

Abstract

The ever-increasing number of lithographic applications for the fabrication of micro-electro-mechanical systems in microsystem technology which require 100 μm and higher photovoltaic materials can not be realized with the conventional positive photoresists. For this application, photo materials are required, which not only form high-build homogeneous layers, but form with high sensitivity structures with a good aspect ratio and vertical profiles with very low micro-roughness and are removable without residue after structural transfer. A process for the preparation and structuring of a UV300 / 400 light-sensitive, high-viscosity, chemically amplified, aqueous-alkaline developable positive photoresist for applications in microsystems technology, which is subsequently removable without residue, is described.

Description

• 1) 35 bis 80 Gew.% einer niedermolekularen, in den Seitenketten säure katalysiert abspaltbare Schutzgruppen enthaltende Polymermatrix und
• 2) 2–30 Gew.% eines lichtempfindlichen Protonensäuregenerators
• 3) gelöst in einem geeignetem Lösemittel/-gemisch enthält, ist zur Herstellung und lithographischen Prozessierung (=Strukturierung) von Schichten von 5 μm bis 2 mm mit einem Aspektverhältnis > 8, die nach erfolgter Strukturübertragung rückstandsfrei entfernbar sind, geeignet.

The invention relates to the production of a UV 300/400 photosensitive, highly viscous, chemically amplified, aqueous-alkaline developable positive-working resist for producing structures for the μm and mm range. The photoreactive material which

• 1) 35 to 80 wt.% Of a low molecular weight, in the side chains acid catalyzed cleavable protecting groups containing polymer matrix and
• 2) 2-30% by weight of a photosensitive proton acid generator
• 3) dissolved in a suitable solvent / mixture is suitable for the production and lithographic processing (= structuring) of layers of 5 microns to 2 mm with an aspect ratio> 8, which are removed without residue after structural transfer, suitable.

The Number of lithographic applications for the production of microelectromechanical Systems in microsystem technology (MST) that require photoresists that 100 μm and higher building Layers form and with very good aspect ratios and a low Micro roughness generate vertical structure profiles is constantly growing. The increased demands on the accuracy / precision of these micromechanical, micro-optical and microfluidic components are usually only with the different variants of the LIGA technique (lithography, Electroplating, impression) by means of X-radiation or UV exposure possible. In order to takes the importance of availability of corresponding photosensitive materials and their simple ones Processing technologies for Applications of the MST market constantly to.

The commercially available Positive photoresists AZ resists (AZ PLP 100/50 (XT), AZ P4000, AZ 9200 series) Fa. Clariant, the SJR 5740 and SPR 220 Fa. of the Fa. Shipley, THB positive of the company JSR Microelectronics and the ma-P 100 of the company. micro resist technology are DNQ / novolac based positive resists with a wide sensitivity at UV 300/400. With these resist systems are in single coating (spincoats) up to 80 micron high layers possible. 100 μm high structurable Layers are obtained only by multiple coating [1-3]. The aqueous-alkaline need developable resists when exposing high layer thicknesses high dose values (long exposure times). The limit of the Durchbelichtbarkeit high layers is due to the lack of transparency at max. 100 μm. For a multiple coating the lithographic process is reversed additional Steps for coating production and drying extended. From a resist height of approx. 60 μm it is no longer possible with these resist systems, that for UV deep lithography to produce necessary vertical profile edges.

Aqueous-alkaline developable negative photoresists consist of a phenolic resin as a polymeric binder and an exposure wavelength and Sensitivity of the resist system determining aromatic bisazide as a photosensitive component dissolved in a solvent or solvent mixture. The transmissibility of these resist systems is due to the phenomenon of Non-bleaching when exposed in the exposure wavelength region on max. 20 μm limited. The achievable resolution is very low at these layer thicknesses and the edges show undercut structure profile, which is suitable for the molding of precise components is unsuitable.

Resist systems based on the concept of chemical amplification (chemically amplified resists = CAR) were used with the purpose of increasing the resolution under the pressure of progressive miniaturization in microelectronics for very small layer thicknesses (<1 μm) for wavelengths in the DUV range and below (193 nm and 157 nm) designed. The height Sensitivity of these resist systems is in the reaction mechanism justified the on exposure and subsequent annealing (post exposure bake = PEB) of the resist layers initiated solubility change in the exposed across from causes the unexposed areas. Upon exposure of such a Resist layer is a proton generated (proton generator = photo acid generator PAG), which in the case of a positive photoresist, a polymer chain cleavage or cleavage of functional groups or in the case of a negative photoresist, a crosslinking reaction the (polymer / oligomer) matrix initiated. As a final product arises in addition to the product with a higher solubility in the developer (= positive resist) or lower solubility (= Negative resist) again a proton, which again a cleavage reaction can go down. A photochemically generated proton goes several times a cleavage or crosslinking reaction. Chemical amplification factors (Number of cleaved side functional groups on the polymer per photolytically generated proton) of up to 50-500 are described. The effectiveness of the fission or crosslinking reaction is due to the polymer / PAG ratio, the Exposure dose and temper conditions affected.

A Variety of chemically amplified working positive photoresists are based on a partially acid labile Groups of substituted polyhydroxystyrene (PHOSt) [4]. PHOSt was due to its transparency and its etch resistance the polymer of the Choice for the development of chemically amplified DUV-248 nm positive resists.

at acetal and ketal substituted PHOSt, representatives of the low activation energy CARs, the cleavage of the acid labile groups takes place spontaneously after or during of the exposure at room temperature. In this case, there is no PEB step necessary [5]. These resist systems often show insufficient linewidth stability as well as low storage stability.

at Copolymers of HOSt and tert-butyl acrylates (tert-BuA), representatives the high activation CARs [4], annealing (= hardening) takes place high temperatures according to the curing concept (= annealing concept) without decomposition of the photographic material.

The Selection of monomers for a polymer is dependent from the functionality of the positive photoresist to be formulated therefrom. So have monomer units acid-labile contain functional groups ("protecting groups") that upon exposure and subsequent annealing (PEB) the solubility change cause. Hydroxyl-containing monomers promote the Substrate adhesion and have an influence on the kinetics of development in aqueous-alkaline Developers. Film forming monomer units promote film formation and increase sometimes the PAG solubility. A small proportion of aromatic monomer units promotes the etching stability of the photosensitive material, but leads also to an increase absorption in the DUV wavelength range. For this reason, cyclic aliphatic groups containing Monomers, instead of the aromatic-containing monomers, in the polymer inserted. By the use of the partially additionally with electrons pulling Group-forming acrylates, e.g. (Iso) bornyl, adamantyl (metha) crylate, In addition to a good Ätzstabilität the high Transparency in the DUV area and lower at exposure wavelengths.

Links, when exposing acid / protons especially the onium salts, special sulfonium and iodonium salts. By appropriate selection of the cation (number and type of aromatics) and of the anion (responsible for the solubility in the resist solvents and for the acidity of the photochemically initiated generated acid) become properties, such as absorption, sensitivity and contrast of the displayed Photographs co-determined. One property of PAGs must be one high thermal stability be, because neither the PAG nor the generated acid may during the annealing process to diffuse out of the layer.

to Avoidance of observed in the processing of positive CARs phenomenon the formation of a T-top or cuticle formation on the structures Beyond the use of protective resist layers or low activation CARs [4,6] also introduced additives into the resist formulation. These additives usually consist of a basic compound in Combination with an acidic compound.

The Use of the concept of chemical amplification for high-build and high-sensitivity photoresists for the The requirements placed on the MST hold great potential in yourself.

It is known to work with photoresists whose photochemical reaction based on a cationic polymerization of epoxidized Bisphenol-A-formaldehyde novolacs occur [7], structures with high aspect ratios and steep edge profiles produced in very high layer thicknesses can be. This after a light exposure and PEB step very strong cross-linking System comes with a solvent developed and is difficult after structural transfer again removable. Due to the high transparency of the layer-forming component and the small amount of acid generator (PAG) in the resist layer thicknesses significantly higher 100 microns in the shortest time durchbelichtbar.

Highly viscous and high-build, UV 300/400 sensitive, easy-to-process, aqueous-alkaline developable positive photoresists for applications in microsystems technology according to the quality requirements of the edge profiles and after the structure has been transferred residue remove, are not yet known.

The object of the invention involves the provision of a UV 300/400 photosensitive, highly viscous, chemically amplified working, aqueous alkaline developable positive photoresist consisting of a low molecular weight matrix, a photosensitive proton acid generator, a solvent or mixture of solvents and layer-forming and / or layer-stabilizing additives, and to provide a process for producing and structuring the resist, wherein the produced resist structure is suitable for forming a Galvanoform for the electrodeposition.

The low molecular weight polymer matrix consists of various monomers in different proportions, each monomer being necessary Function in the resist (acid-labile Protecting groups, substrate adhesion promoting Hydroxyl groups, etch resistance increasing Aromatics, layer former) is responsible. The co, ter or Tetrapolymers are in an easy to carry out polymerization under Addition of a radical initiator produce. The low molecular weight polymeric compounds are acetone soluble, which is a light Removal of the resist after the structure transfer permits. The low solubility the low molecular weight polymeric compounds in aqueous solutions with an extremely acidic to extremely basic pH range is from great advantage for the electrodeposition of metals in the context of the LIGA process.

Of the Solids content of the resist solution may be due to the low molecular weight of the polymers used be set very high. The resist solution shows a very high viscosity and forms homogeneous layers.

suitable Photostarter for the cationic cleavage of the acid labile functional groups (protecting groups) are known initiators, such as. Sulfonium, iodonium and phosphonium salts which are the polymer solution in Concentrations of 2-30 % By weight, preferably 3-15 % By weight added become. Common are triarylsulfonium hexafluoroantimonate, hexafluorophosphate or also mixtures of triarylsulfonium hexafluoroantimonate and thiophenoxytriarylsulfonium hexafluoroantimonate, under the trade name UVE of the company General Electric Company or UVI-6974 and UVI 6990 from Union Carbide commercial for disposal stand. The resist layers are in the spectral range UV 300/400 sensitive and can with high pressure lamps, Lasers and X-ray sources be exposed.

By the high transparency of the polymer matrix in the exposure wavelength range in conjunction with the chemical amplification reaction mechanism, layers can be used be structured in high thicknesses.

Of the Use of non-reactive plasticizers in the resist allows voltage and crack-free high-build structurable layers. The use of a buffer system in The resist prevents the formation of structures with a T-top.

Advantageous is the use of non-toxic solvents in the resist. The selected material combinations be in organic solvents, e.g. Propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), anisole solved and the coating is carried out by conventional processing techniques, such as e.g. Spin-coating, knife-coating or pouring.

To the exposure and a subsequent annealing step is a solubility produced on the polymer matrix, which is a development in aqueous-alkaline solutions allows. From great The advantage is the use of environmentally friendly developers on aqueous Base.

Of the Resist described in the invention is suitable in lithographic Process structures from 5 μm to 2 mm thickness with an aspect ratio of> 8 to produce the high dimensional stability (1: 1 transmission of the Structure of mask in resist), a high edge steepness up to 89 ° and have a low edge roughness and is suitable for a stable requirement for to represent a galvanic impression.

The Invention will be explained in more detail with reference to the following embodiments.

polymer syntheses

For the used Monomers became the following abbreviations selected: Methyl / butyl methacrylate - M / BuMA, Methacrylic acid - MAA, tert-butyl methacrylate - tert-BuMA / tert-BuA, styrene - St. Als Initiator was 2,2'- Azobisisobutyronitrile - AIBN used.

example 1

Synthesis of poly (tert-BuMA / MAA / St)

6.75 g of tert-BuMA, 5.45 g of MAA, 4.94 g of styrene and 1.04 g of AIBN are dissolved in 170 g of acetone in a 3-necked flask equipped with stirrer, reflux condenser and inert gas. After 20 hours of stirring under reflux and inert gas atmosphere (nitrogen), the polymer is obtained by precipitating the clear, colorless, higher-viscosity reaction solution in water, filtered off with suction and dried. The polymer is purified by reprecipitation of an acetone solution in water, filtered off and dried in vacuo at 70 ° C.
Yield: 12.0 g (70.1%), white powder, Mw: 8 550 g / mol, T _g : 101 ° C, T _d : 246 ° C, mp: 155-158 ° C

Example 2

Synthesis of poly (tert-BuA / MAA / MMA / St)

The method of synthesis is analogous to that of Example 1, using the following monomers and proportions in the monomer mixture: Using 15 g of tert-BuA, 6.72 g of MAA, 7.8 g of MMA, 12.18 g of styrene and 2.4 g of AIBN in 315 g of acetone, after a reaction time of 26.8 g, 22.8 g (yield 54.7%) of a white powder are obtained.
Mw: 9100 g / mol, T _g: 101 ° C, T _d: 252 ° C, mp: 126-129 ° C

Example 3

 Synthesis of poly (tert-BuA / MAA / BuMA / St)

The method of synthesis is analogous to that of Example 1, using the following monomers and proportions in the monomer mixture: Using 15 g of tert-BuA, 6.72 g of MAA, 11.1 g of BuMA, 12.18 g of styrene and 2.40 g AIBN in 315 g of acetone are obtained after 26 h reaction time 28.7 g (yield 63.8%) of a white powder.
Mw 10 500 g / mol, _Tg: 95 ° C, T _d: 250 ° C, mp: 97-101 ° C

Example 4

Synthesis of poly (tert-BuMA / MAA / MMA / St)

The method of synthesis is analogous to that of Example 1, using the following monomers and proportions in the monomer mixture: Using 25 g of tert-BuMA, 8.65 g of MAA, 10.06 g of MMA, 13.08 g of styrene and 3.09 g AIBN in 400 g of acetone are obtained after 26 h reaction time 52.97 g (yield 93.3%) of a white powder.
Mw: 8000 g / mol, T _g: 107 ° C, T _d: 252 ° C, mp: 118-121 ° C

at the resist approaches be for the solvents and the accessories following abbreviations used: propylene glycol monomethyl ether acetate - PGMEA, propylene glycol monomethyl ether - PGME, Methoxybenzene / anisole - MOB, Cyclohexanone - CH, Triethanolamine - TEA, Salicylic acid - Sasr, IPA - isopropyl alcohol.

Example 5

Resist rate 1

In 75 g of a solvent mixture (PGMEA: MOB: CH = 80: 10: 10 [in% by weight]), added with 0.6 g of a polyether-modified Polydimethylsiloxane, 0.19 g TEA, 0.17 g Sasr and 7.5 g of a non reactive plasticizer is 75 g of poly (tert-BuMA / MAA / MMA / St) solved. In the clear solution will be afterwards 19.5 g of an onium salt solution stirred. 150 g of resist with a solids content of 50% by weight are obtained.

Example 6

Resist rate 2:

In 75 g of a solvent mixture (PGMEA: MOB: CH = 80: 10: 10 [in wt.%]), Mixed with 0.37 g of a polyether-modified polydimethylsiloxane and 2.25 g of a non-reactive plasticizer, 75 g of egg Partially tert-butyloxycarbonyl-substituted phenolic resin (prepared according to known synthesis instructions [8]). 15 g of an onium salt solution are subsequently stirred into the clear solution. 150 g of resist with a solids content of 50% by weight are obtained.

Example 7

Resistance Theorem 3:

In 75 g of a solvent mixture (PGMEA: PGME = 70:30 [in% by weight]), added with 0.375 g of a polyether-modified Polydimethylsiloxane, 0.19 g TEA, 0.17 g Sasr and 3.75 g of a non reactive plasticizer 75 g of poly (tert-BuA / HOSt / St) are dissolved. In the clear solution will be afterwards 11.25 g of an onium salt solution stirred. 150 g of resist with a solids content of 50% by weight are obtained.

Example 8

Tab.).4 '' silicon wafers prepared as adhesion promoters with HMDS are spin-coated for 60 s with a resist according to Example 5. The resulting layers are oven-dried at 90 ° C. and then image-wise exposed to UV300 / UV400, then heat-treated at 120 ° C. (ramp of 80 ° C.) and developed in 0.2 N NaOH (

Tab.).

Example 9

Tab.).4 '' silicon wafers prepared as adhesion promoters with HMDS are spin-coated for 60 s with a resist according to Example 6. The resulting layers are oven dried at 90-100 ° C and then exposed imagewise with UV300 / UV400, then annealed at 125 ° C and developed in 0.25 N NaOH with IPA additive (

Tab.).

Example 10

Tab.).4 '' silicon wafers prepared as adhesion promoters with HMDS are spin-coated for 60 s with a resist according to Example 7. The resulting layers are oven dried at 95 ° C. and then exposed imagewise to UV300 / UV400, then annealed at 120 ° C. (ramp of 80 ° C.) and developed in 0.15 N NaOH (

Tab.).

Example 11

Electroplating with Resist 1

In a Galvanoform of Resist 1 with a layer thickness of 48 microns accordingly Example 8 on a gold-coated substrate becomes nickel in a nickel sulfamate bath (pH = 3.5) at a temperature of 55 ° C and at 300-400 mA galvanic with a height of 30 μm deposited and the resist then removed with acetone.

Example 12

Electroplating with Resist 3

In a Galvanoform of Resist 3 with a layer thickness of 50 microns accordingly Example 10 on a gold-coated substrate becomes nickel in a nickel sulfamate bath (pH = 3.5) at a temperature of 55 ° C and at 300-400 mA galvanic with a height of 45 μm deposited and the resist then removed with acetone.

Claims (13)

Process for preparation and structuring UV300 / 400 photosensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating, characterized in that - the resist, which is a low molecular weight Polymer matrix that catalyzes in the side chain acid cleavable protecting groups contains a photosensitive acid generator, a solvent or solvent mixture and layering and / or layer stabilizing additives - the resist applied as a layer on the substrate, dried, imagewise in the wavelength range from 200-500 nm exposed, tempered, with an aqueous alkaline developer is developed and - the lithographically generated resist structures for the production of galvanic molded structures in the range of 5 microns to 2 mm used and then again be removed. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist is one in the side chains catalyzed by acid cleavable protecting group-containing polymer matrix having a molecular weight of up to 20,000 g / mol. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist is a matrix 2-4 different Monomer units consisting of 20-75% acid catalyzes cleavable Protecting groups containing, 10-35% adhesion to substrates promotional Containing OH groups, 10-50 % Aromatics containing and 10-50% layer forming monomer units are although monomer units several functions in itself unite, contains. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist has a solids content from 35-80 % By weight of the low molecular weight polymer matrix. Process for producing and structuring a UV300 / 400 light-sensitive, aqueous-alkaline developable, highly viscous chemically amplified positive photoresist for applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist as photosensitive acid generator is an alkyl-aryl onium salt of the general formula I in which O is a sulfonium, iodonium ion, R ¹ , R ² , R ^{3 are} branched and unbranched alkyl / aryl or alkyl- and aryl-substituted aromatics and X is, for example, hexafluoroantimonate, hexafluorophosphate, trifluoromethanesulfonate stand.

Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist has a content of photosensitive acid generator from the solid of 2-30 % By weight. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist as a solvent esters, ketones, alcohols, Containing aromatics or mixtures thereof. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the resist as a layer-forming and / or layer stabilizing additives Surfactants, smoothers, Adhesion promoters, non-reactive plasticizers and a base quenching agent System contains. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that in the layer production layers in the range 5 μm up to 2 mm by means of spin coating, dipping, rollercoats or Casting (molding) be generated. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that for the exposure of the resist layers High pressure lamps, Laser or X-ray be used. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that for the development of the exposed and annealed layers containing alkali metal ion-containing developers with a concentration of 0.2 wt.% To 1.5 wt .-% or metal ion-free Developer with a concentration 1 wt.% Used to 5 wt.% become. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the lithographically produced resist structures for the production of electroformed structures in baths with a pH of 1 to 13 at temperatures from room temperature to 80 ° C. are. Process for the preparation and structuring of a UV300 / 400 light-sensitive, aqueous-alkaline developable, high-viscosity chemically reinforced Positive photoresist for Applications in microsystems technology, in particular for microplating according to claim 1, characterized in that the lithographically produced resist structures after the galvanic impression residue free are removable.